Resistance welding or electric resistance welding is a welding process, such as spot and seam welding, in which heat to form the weld is generated by the resistance of the welding current through the workpieces. Spot resistance welding may be used to join two or more overlapping metal workpieces, such as metal sheets. Electrodes are simultaneously used to clamp the workpieces together and to pass current through the workpieces. When the current is passed between the electrodes, heat is generated due to the higher electrical resistance where the surfaces of the workpieces contact each other. The electrodes, or the ends of the electrodes, are usually formed from conductive materials, such as copper or copper alloys.